This is motivated by some upcoming patch by Heňo.
* spot/twaalgos/sccinfo.hh (edges_of, inner_edges_of): New methods.
* spot/twaalgos/sccinfo.cc, spot/twaalgos/strength.cc: Use them.
* spot/twa/twagraph.hh (edge_number): Add an overload.
* python/spot/impl.i: Bind the new methods.
* tests/python/sccinfo.py: Add tests.
* NEWS: Mention the changes.
Related to #172, where we discussed that scc_info bindings were
missing.
* spot/twaalgos/sccinfo.hh (spot::scc_info::scc_node): Move...
(spot::scc_info_node): ... here to help Swig.
* python/spot/impl.i: Add bindings for scc_info.
* tests/python/sccinfo.py: New file.
* tests/Makefile.am: Add it.